{"record":{"id":"87136e1ffc5b4f93","repo":"hyperledger/fabric","slug":"error-writing-output","errorCode":null,"errorMessage":"error writing output","messagePattern":"error writing output","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"cmd/configtxlator/main.go","lineNumber":156,"sourceCode":"\t}\n\tmsg := reflect.New(msgType.Elem()).Interface().(proto.Message)\n\n\terr = protolator.DeepUnmarshalJSON(input, msg)\n\tif err != nil {\n\t\treturn errors.Wrapf(err, \"error decoding input\")\n\t}\n\n\tif msg == nil {\n\t\treturn errors.New(\"error marshaling: proto: Marshal called with nil\")\n\t}\n\tout, err := proto.Marshal(msg)\n\tif err != nil {\n\t\treturn errors.Wrapf(err, \"error marshaling\")\n\t}\n\n\t_, err = output.Write(out)\n\tif err != nil {\n\t\treturn errors.Wrapf(err, \"error writing output\")\n\t}\n\n\treturn nil\n}\n\nfunc decodeProto(msgName string, input, output *os.File) error {\n\tmt, err := protoregistry.GlobalTypes.FindMessageByName(protoreflect.FullName(msgName))\n\tif err != nil {\n\t\treturn errors.Wrapf(err, \"error encode input\")\n\t}\n\n\tmsgType := reflect.TypeOf(mt.Zero().Interface())\n\n\tif msgType == nil {\n\t\treturn errors.Errorf(\"message of type %s unknown\", msgType)\n\t}\n\tmsg := reflect.New(msgType.Elem()).Interface().(proto.Message)\n","sourceCodeStart":138,"sourceCodeEnd":174,"githubUrl":"https://github.com/hyperledger/fabric/blob/2736b63f8fd5932511d56fe68b7039d15977f7f6/cmd/configtxlator/main.go#L138-L174","documentation":"In `encodeProto` (cmd/configtxlator/main.go:156), writing the marshaled protobuf bytes to the `--output` file failed. The proto content is fine; the failure is at the file I/O layer (unwritable path, missing directory, permissions, full disk). configtxlator wraps the OS error as 'error writing output'.","triggerScenarios":"Running `configtxlator proto_encode --output /some/path` where the path's directory doesn't exist, the file lacks write permission, the path is a directory, or the filesystem is full/read-only.","commonSituations":"Pointing --output at a nonexistent directory; running inside a container with a read-only mount; permission mismatch when running as a different user; reusing a path that is actually a directory.","solutions":["Create the output directory first (mkdir -p) or point --output at an existing writable directory.","Check file/directory permissions for the user running configtxlator.","Verify the path is a file, not a directory, and the filesystem is not read-only or full (df / mount).","Run with the full OS error visible (the wrapped message includes the underlying cause) to target the exact I/O problem."],"exampleFix":"// before\n$ configtxlator proto_encode --type common.Config -i config.json -o /nonexistent/dir/config.pb\n// after\n$ mkdir -p ./artifacts && configtxlator proto_encode --type common.Config -i config.json -o ./artifacts/config.pb","handlingStrategy":"validation","validationCode":"// Ensure the output directory exists and is writable before invoking configtxlator\nimport os\nout_path = './artifacts/config.pb'\nout_dir = os.path.dirname(out_path) or '.'\nos.makedirs(out_dir, exist_ok=True)\nif not os.access(out_dir, os.W_OK):\n    raise SystemExit(f'{out_dir} is not writable')","typeGuard":null,"tryCatchPattern":"out, err := exec.Command(\"configtxlator\", \"proto_encode\", ..., \"--output\", outputPath).CombinedOutput()\nif err != nil && strings.Contains(string(out), \"error writing output\") {\n\treturn fmt.Errorf(\"cannot write %s (check dir exists, perms, disk space): %s\", outputPath, out)\n}","preventionTips":["mkdir -p the output directory in scripts before running configtxlator.","Use relative paths inside the container's writable workspace, not host-only mounts.","Check disk space and read-only mounts in CI/container environments.","Verify the output path is a file, not an existing directory."],"tags":["hyperledger-fabric","configtxlator","file-io","filesystem"],"backgroundTag":"file-write-failed","analyzedSha":"2736b63f8fd5932511d56fe68b7039d15977f7f6","analyzedAt":"2026-09-04T08:52:36.465Z","contentChangedAt":"2026-09-04T08:52:36.465Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}